BioTrojans: viscoelastic microvalve-based attacks in flow-based microfluidic biochips and their countermeasures.

Area of Science:

• Biomedical Engineering
• Cybersecurity
• Materials Science

Background:

• Flow-based microfluidic biochips (FMBs) are crucial for research and diagnostics.
• The security of FMBs against material-level cyber-physical attacks is an emerging concern.
• Polydimethylsiloxane (PDMS) microvalves are key FMB components vulnerable to chemical tampering.

Purpose of the Study:

• To demonstrate a novel material-level cyber-physical attack on PDMS microvalves.
• To characterize the vulnerability of tampered microvalves to mechanical stress.
• To propose security measures against such attacks.

Main Methods:

• Altering the PDMS curing ratio to create chemically tampered "BioTrojan" microvalves.
• Subjecting authentic and BioTrojan microvalves to low-frequency actuations (2 Hz).
• Utilizing Dynamic Mechanical Analysis (DMA) and finite element analysis (FEA) for material characterization.

Main Results:

• BioTrojan valves (30:1 and 50:1 curing ratios) ruptured rapidly under 2 Hz actuation.
• Authentic valves (10:1 ratio) remained intact after 2 days (345,600 cycles) of actuation.
• BioTrojan valves store significantly more mechanical energy, leading to rupture susceptibility.

Conclusions:

• Chemically altered PDMS microvalves present a new cyber-physical security threat ("BioTrojans").
• Security-by-design approaches like peripheral fillets can mitigate stress concentration.
• Spectral authentication using fluorescent microvalves can detect BioTrojan attacks.